Congratulations!  I remember my first game that I ran and I remember having the same concerns.  I am still pretty green myself and am starting to put together a campaign for the Dresden RPG.

Some tips given to me that I found very useful:
-The GM is always right.  If it comes down to an argument, use your best judgment and make the call.  If they don't like it, they can talk to you about it later. 
-If they get a little side tracked, its ok.  Like some others have said, just ad lib and get creative.  See if there is a way you can tie them back into your storyline with bread crumbs rather than a Fate road sign that they crash into.  I have found on many occasions that most players don't like it when you try to keep them on a specific path.  Most people tend to feel a little beaten over the head with the plot. 
-Be the best chess player ever!  Plan at least 10 moves ahead.  IE, try to plan out a number of different reactions your group might have a head of time.  Be prepared for several options and what you would do with it.  Ask yourself if your villains would have contingency plans an if so, which ones would they have and what wouldn't they be prepared for?  It is difficult, but you are less likely to be caught by surprise.  When my players would still surprise me in fun and creative ways that were impressive, I would reward them ^_^. 
-A little confusion and misdirection is fun!  It keeps the players guessing.
-There is no such thing as just good and evil.  It is a lot of fun to throw in a lot of gray to the scale.  People who are helpful but think how you are doing things is wrong and who try to work against you.  People who have ulterior motives but you can't tell they are ready to stab you in the back because their smile is just so friendly.  People who live for drama and chaos and just like to throw a wrench into the workings because its fun to see the mess after...

Have fun!

I tried to post this earlier and for some reason it didn't work   

I have been looking around to join a Dresden game, but to no avail.  There aren't any groups currently playing that I can find, and those who are interested in running a game are either currently running a different system, or are nowhere near being close enough to running one.  So yesterday afternoon I was struck by lightening and an entire story line created itself in my head in less than a minute.  That was fun.  It is a relatively short story line that shouldn't run more than 12 games (hopefully), but I still need some help.  I need a bunch of weird/scary/random/disturbing dreams:  10 per player would be nice.  I will probably have at least 5 players so that means I need 50 dreams...PLEASE HELP!  I want to have them all written out and ready before I start the game.  Don't get me wrong, I have a number of my own that I am throwing in the mix, but being overly prepared is a lot better than having to come up with so many dreams all on my own.

I don't want to go into too much detail of the game right now because I know at least 2 possible players frequent these boards.  However, I would be happy to share what starts to happen and I would also be more than happy to share my notes in the future with people who are interested and who have shared their dreams.  This game has a definite beginning, middle and distinct end, whither or not the players succeed... Muahahaha!  For once I get to be a creepy DM with plots and plans of doom ^_^!  I still want to play in a game, but this will have to do for now.

I am really enjoying all of the different ideas from people.  I have to say that I just love games with sound tracks.  What about if you had it happening with different bands? Lets say there is a Cult that worships dark power X.  Each member of the cult is a stage hand or a sound director.  As the band is playing, there is a subsonic (or something) recorded ritual that takes about the same amount of time to finish as it does to play 7 songs.  Whenever the end of the ritual happens, it triggers the energies and concepts of the song currently being played.  The sound director would know the playlist and could plan out which song he/she wanted to be triggered.  They could also make subtle suggestions which order the songs should be played in.  The energy of the audiance would feed the generation of the ritual.  This could be happening for any number of local bands (if you make it local, then you don't have to worry about a touring band).  You could also have some mishaps where the crowd begs for a song in the middle of the play list, which would mess things up a bit for cult X (not everything goes right for the bad guys all the time, no matter how well they plan).  This way, it might make it a little harded to track down, but it might also have the problem of being more convoluted. 

Songs: 
Lights Out- Breaking Benjamin      Red Court vamps take a night rampage out on the town  (PCs might have heard that the vamps were planning something like this but they didn't know when it was going to happen)
Drive- Incubus  No reports of any DUIs and a mass drop in unemployment (oops ^_^)
Possibly something from Pearl Jam?
Perhaps something from Disturbed?